Project Summary The overall goal of this proposal is to elucidate the molecular mechanisms of AMPA receptor (AMPAR) trafficking in the context of excitatory synaptic transmission and plasticity. This five-year career development program is designed to prepare the candidate of this K99/R00 Pathway to Independence Award, Dr. Javier Diaz Alonso, for an independent scientific career. It will build on Dr. Diaz?s background in synaptic transmission and plasticity, while expanding his toolbox in electrophysiology, molecular biology and biochemistry. Dr. Diaz is a postdoctoral fellow with Dr. Roger Nicoll at UCSF. The training program will take place under the guidance of Dr. Nicoll, who has outstanding mentoring experience. He will oversee Dr. Diaz?s scientific progress, while preparing him for the transition to an independent career. Long-term potentiation (LTP), where repetitive stimulation of afferents results in the accumulation of AMPAR in the postsynapse, is by far the most studied form of synaptic plasticity, and is considered the most compelling model explaining the cellular and molecular basis of learning and memory formation. Considerable progress in the understanding of this process has been achieved, but fundamental issues remain to be elucidated. This proposal will explore 3 fundamental questions about AMPAR trafficking in the context of LTP: 1) What is the relative contribution of AMPAR exocytosis vs lateral diffusion in LTP? Together with his mentor and advisor Dr. Michael Tadross, Dr. Diaz has designed a novel tool that will enable the disambiguation of the contribution of exocytosed AMPAR during LTP. 2) What is the role of the extracellular amino-terminal domain (ATD) of AMPAR subunits and its interactions with synaptic cleft proteins? In this proposal, Dr. Diaz will dissect the roles of the extracellular domains of various AMPAR subunits, and identify the synaptic cleft proteins that interact with them, following a series of proteomic approaches that have been delineated in close collaboration with advisors Dr. Katherine Roche and Dr. Alma Burlingame. 3) What is the role of the cytoplasmic carboxy-terminal domain (CTD) in AMPAR trafficking during LTP? Dr. Diaz will undertake several experimental approaches to rigorously determine whether recent results supporting a ?CTD-centric? model of AMPAR trafficking during LTP and previous observations supporting a major role for the ATD are reconcilable. This is an essential requirement for the LTP field to move forward. Dr. Diaz?s long-term career goal is to lead an independent research laboratory in basic neuroscience as a tenured-track principal investigator in an academic research institution. He will apply a multidisciplinary approach combining biochemistry, cellular and molecular biology, imaging and electrophysiology, together with genetic manipulations to establish a unique research line aimed at understanding the mechanisms that govern synaptic transmission, underlie synaptic plasticity and give rise to neurological disease.